Characterizing the High Isomeric Complexity of Bio-Oils Derived from Biomass Pyrolysis Using Liquid Chromatography Hyphenated with 18 T Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry

Lignocellulosic biomass is the most abundant type of renewable feedstock. It can be used to produce bio-oils, often by pyrolysis processes. Depending on the treatment and feedstocks used, the bio-oils obtained present very different molecular compositions, influencing their upgrading process into biofuels. As they are highly complex mixtures, their molecular characterizations are challenging. One way, among others, is to probe their molecular level by using direct infusion in Fourier transform ion cyclotron mass spectrometry (FTICR MS). However, mass spectrometry alone cannot discriminate between isomers, and a loss of information because of ionization competition can be observed. Hyphenation of liquid chromatography (LC) with FTICR MS can afford an efficient solution to these issues but requires compromises, mainly on the MS side. In this work, we evaluated the performance of a new 18 T FTICR MS coupled to reversed-phase liquid chromatography for the characterization of bio-oils. Using representative standards of different molecular families (carbohydrates, polyphenols, acids, etc), a method adapted to bio-oils was developed in LC-FTICR MS. The coupling demonstrated the high mass-accuracy stability of FTICR MS even under high total ion current variations and revealed the very high isomeric complexity of bio-oils. Additionally, the coupling reduced ionization competition, enabling the detection of compounds that could not be detected by direct injection. Finally, four bio-oils were compared to highlight the interest of the proposed method.